Hey Gary,
An IPO - Initial Public Offering - is when a private company lists its shares publicly for the first time. In essence, they apply to list on a stock exchange, like the TSX vis prospectus which details a bunch of stuff about the company. There are prescribed information that the company must fill in, and that is usually accompanied by additional marketing information. There are different types of IPOs, but the most common is when the company values itself at a certain market cap, and looks to raise money inline with that market cap. That is how the pricing is set.
Usually, institutional investors make up the majority of investment in an IPO before it lists and being trading publicly. Retail investors do have the opportunity do also do so through their brokrage, but often times they don't get filled. Which means, there was more demand for the IPO that there were shares available. Personally, i've tried about half a dozen times and have never been filled.
That is it in a nutshell- there are so many more complications around it, but in effect that's what it is. An IPO reflects the company's intention to list publicly on an exchange. The majority of IPOs proceed and once the shares are listed, the IPO is effectively complete. Other times, the company will halt the IPO likely a sign of poor demand or negative market sentiment. We've seen that a few times lately.
If you have any other specific questions, let me know .
Mat